Over expression of ubiquitin-conjugating enzyme E2O in bone marrow mesenchymal stromal cells partially attenuates acute myeloid leukaemia progression

Bone marrow mesenchymal stromal cells (BM-MSCs) are implicated in the pathogenesis of acute myeloid leukaemia (AML). However, due to the high heterogeneity of AML the mechanism underlying the cross-talk between MSCs and leukaemia cells is not well understood. We found that mixed-lineage leukaemia-AF9 (MLL-AF9)-induced AML mice-derived MSCs had higher proliferative viability compared to wild-type mice-derived MSCs with ubiquitin-conjugating enzyme E2O (Ube2o) down-regulation. After overexpression of UBE2O in AML-derived MSCs, the growth capacity of MSCs was reduced with nuclear factor kappa B subunit 1 (NF-κB) pathway deactivation. In vitro co-culture assay revealed that UBE2O-overexpression MSCs suppressed the proliferation and promoted apoptosis of AML cells by direct contact. In vivo results revealed that the leukaemia burden was reduced and the overall survival of AML mice was prolonged, with decreased dissemination of leukaemia cells in BM, spleen, liver and peripheral blood. Additionally, subcutaneous tumorigenesis revealed that tumour growth was also suppressed in the UBE2O-overexpression MSCs group. In conclusion, UBE2O was expressed at a low level in MLL-AF9-induced AML mice-derived MSCs. Overexpression of UBE2O in MSCs suppressed their proliferation through NF-κB pathway deactivation, which resulted in AML suppression. Our study provides a theoretical basis for a BM microenvironment-based therapeutic strategy to control disease progression.     

Spontaneous remission in acute myeloid leukaemia

A summary of the literature of adult patients with acute myeloid leukaemia (AML) who have undergone spontaneous remission (SR) is presented together with a report of a patient whose SR was accompanied by cytogenetic remission. There are less than 20 reports of SR since the 1980s. SR is by no means synonymous with cure, since the average duration of the remission is only 7·1±9·2 months. Neither infections nor transfusions are absolute requirements of SR.     

Neoplastic circulating endothelial-like cells in patients with acute myeloid leukaemia

Accumulating evidence suggests that angiogenesis may play a key role in the pathogenesis of leukaemic disorders. Several studies have shown that bone marrow-derived endothelial cells (EC) may contribute to tumour angiogenesis and that in the peripheral blood of cancer patients there is an increased amount of circulating ECs (CECs) that may participate to new vessel formation. In this report, we showed that, in seven acute myeloid leukaemia (AML) patients with known cytogenetic abnormalities, CEC levels were significantly increased in comparison with controls and that a significant proportion of these CECs carried the same chromosomal aberration as blast cells (20-78%, mean value 42.1% of CECs). Most of CECs (mean value 74.4%) displayed immunophenotypic features of endothelial progenitor cells as they expressed CD133, a marker gradually lost during EC differentiation and absent on mature EC. These findings suggest a possible direct contribution of AML-related CECs to tumour vasculogenesis and possibly to the spreading and progression of the disease.     

Single agent thalidomide in patients with relapsed or refractory acute myeloid leukaemia

Thalidomide is a putative anti-angiogenesis agent that has significant anti-tumour activity in haematological malignancies with increased bone marrow angiogenesis, including multiple myeloma (MM) and myelodysplastic syndromes (MDS). Increased levels of the mitogen for angiogenesis, vascular endothelial growth factor (VEGF), correlate with worse survival in acute myeloid leukaemia (AML). A phase II trial of thalidomide was conducted in patients with relapsed- or refractory-AML previously treated with cytarabine-containing regimens. A total of 16 patients with refractory- or relapsed-AML were treated with thalidomide 200-800 mg orally daily (median dose 400 mg daily) for a median of 27 d (range, 3-94 d). Overall, one patient (6%) achieved complete remission (CR) lasting for 36 months, and two patients had a transient reduction in marrow blasts from 8% and 7% to less than 5% in both cases. There was no correlation between reduction in levels of angiogenesis markers and response. Toxicities related to thalidomide were significant, and precluded dose escalation beyond 400 mg orally daily in most patients. Although there appears to be some evidence of biological activity, single agent thalidomide is not an optimal choice of therapy for salvaging patients with relapsed- or refractory-AML. Thalidomide analogues with more potent immunomodulatory activities and more favourable toxicity profiles may offer more promise as anti-AML therapy.     

Abemaciclib drives the therapeutic differentiation of acute myeloid leukaemia stem cells

Self-renewal and differentiation arrest are two features of leukaemia stem cells (LSCs) responsible for the high relapse rate of acute myeloid leukaemia (AML). To screen drugs to overcome differentiation blockade for AML, we conducted screening of 2040 small molecules from a library of United States Food and Drug Administration-approved drugs and found that the cyclin-dependent kinase (CDK)4/6 inhibitor, abemaciclib, exerts high anti-leukaemic activity. Abemaciclib significantly suppressed proliferation and promoted the differentiation of LSCs in vitro. Abemaciclib also efficiently induced differentiation and impaired self-renewal of LSCs, thus reducing the leukaemic cell burden and improving survival in various preclinical animal models, including patient-derived xenografts. Importantly, abemaciclib strongly enhanced anti-tumour effects in combination with venetoclax, a B-cell lymphoma 2 (Bcl-2) inhibitor. This treatment combination led to a marked decrease in LSC-enriched populations and resulted in a synergistic anti-leukaemic effect. Target screening revealed that in addition to CDK4/6, abemaciclib bound to and inhibited CDK9, consequently attenuating the protein levels of global p-Ser2 RNA Polymerase II (Pol II) carboxy terminal domain (CTD), Myc, Bcl-2, and myeloid cell leukaemia-1 (Mcl-1), which was important for the anti-AML effect of abemaciclib. Collectively, these data provide a strong rationale for the clinical evaluation of abemaciclib to induce LSC differentiation and treat highly aggressive AML as well as other advanced haematological malignancies.     

Characteristics and outcome of primary resistant disease in paediatric acute myeloid leukaemia

A significant proportion of events in paediatric acute myeloid leukaemia (AML) are caused by resistant disease (RD). We investigated clinical and biological characteristics in 66 patients with RD from 1013 children with AML registered and treated according to the NOPHO-AML 93, NOPHO-AML 2004, DB AML-01 and NOPHO-DBH AML 2012 protocols. Risk factors for RD were age10 years or older and a white-blood-cell count (WBC) of 100 × 10⁹/L or more at diagnosis. The five-year overall survival (OS) was 38% (95% confidence interval [CI]: 28%–52%). Of the 63 children that received salvage therapy with chemotherapy, 59% (N = 37) achieved complete remission (CR) with OS 57% (95% CI: 42%–75%) compared to 12% (95% CI: 4%–35%) for children that did not achieve CR. Giving more than two salvage chemotherapy courses did not increase CR rates. OS for all 43 patients receiving allogeneic haematopoietic stem cell transplantation (HSCT) was 49% (95% CI: 36%–66%). Those achieving CR and proceeding to HSCT had an OS of 56% (95% CI: 41%–77%, N = 30). This study showed that almost 40% of children with primary resistant AML can be cured with salvage therapy followed by HSCT. Children that did not achieve CR after two salvage courses with chemotherapy did not benefit from additional chemotherapy.     

Phase I/II study of vaccination with dendritic-like leukaemia cells for the immunotherapy of acute myeloid leukaemia

Twenty-two patients with acute myeloid leukaemia were recruited into a phase I/II clinical trial investigating the vaccination of patients in complete remission (CR) with autologous dendritic-like leukaemia cells (DLLC). At trial entry, leukaemia cells were harvested and tested for their ability to undergo cytokine-induced dendritic cell differentiation. Patients were then treated with intensive chemotherapy. Five patients achieved both CR and had leukaemia cells that successfully underwent differentiation and therefore proceeded to vaccination. Four escalating doses of DLLC were administered weekly by subcutaneous injection. Vaccination was generally well tolerated although one patient developed extensive eczema and an increased antinuclear factor titre possibly indicating induction of autoimmunity. Development of anti-leukaemic T-cell responses was assessed by enzyme-linked immunospot analysis of gamma-interferon secreting T lymphocytes and by human leucocyte antigen tetramer analysis for WT1-specific T cells. Increases in anti-leukaemic T-cell responses were demonstrated in four patients, but only two of the five remained in remission more than 12 months postvaccination. The study has demonstrated that generation of DLLC is feasible in only a subgroup of patients and is currently neither broadly applicable or clinically effective.     

Isolated gingival relapse in acute myeloid leukaemia

A 47-yr-old man with acute myeloid leukaemia had been in complete remission for 18 months when he developed a gingival tumour. Histological examination revealed leukaemic infiltrate and, at this stage, no other signs of relapse could be demonstrated. Chemotherapy and local radiotherapy resulted in the disappearance of the mass; however, histological abnormalities persisted. First relapse of acute myeloid leukaemia presenting as a gingival tumour has not been previously reported.     

Quantitative expression of thrombopoietin receptor on leukaemia cells from patients with acute myeloid leukaemia and acute lymphoblastic leukaemia

Using a non-isotopic ligand binding assay, we quantitatively examined the amount of human thrombopoietin (TPO) receptor (TPO-R) on leukaemia cells from 128 patients with acute myeloid leukaemia (AML) or acute lymphoblastic leukaemia (ALL). The TPO-R was expressed in 53 (47%) of 114 AML cases, and an in vitro treatment with TPO led to proliferation (stimulation index >1.5) of leukaemia cells in 13 (20%) of 66 AML cases examined. The TPO levels had no relation to the FAB classification except for FAB-M7 AML. All five FAB-M7 cases expressed TPO-R, and one of three FAB-M7 examined showed in vitro proliferative response to TPO. Although there was no significant correlation ( r  = 0.3125) between the amount of TPO-R and the proliferative response, all of the AML cases which showed the in vitro response had TPO-R expression. There was no relationship between TPO-R amount and CD phenotypes, or the amount of granulocyte-colony stimulating factor (G-CSF) receptor. TPO-R was also expressed in two (14%) of 14 cases of ALL, and only these two cases had in vitro proliferative response to TPO. One had only lymphoid antigens, and the other had both lymphoid and myeloid antigens. Our results suggest that some leukaemia cells express functionally active TPO-R.     

Bone marrow mesenchymal stromal cells non-selectively protect chronic myeloid leukemia cells from imatinib-induced apoptosis via the CXCR4/CXCL12 axis

Background

Residual chronic myeloid leukemia disease following imatinib treatment has been attributed to the presence of quiescent leukemic stem cells intrinsically resistant to imatinib. Mesenchymal stromal cells in the bone marrow may favor the persistence and progression of leukemia by preserving the proliferation and self-renewal capacities of the malignant progenitor cells.

Design and Methods

BV173 or primary chronic myeloid leukemia cells were co-cultured with human mesenchymal stromal cells and imatinib-induced cell death was then measured. The roles of pro-and anti-apoptotic proteins and chemokine CXCL12 in this context were evaluated. We also studied the ability of BV173 cells to repopulate NOD/SCID mice following in vitro exposure to imatinib and mesenchymal stromal cells.

Results

Whilst imatinib induced dose-dependent apoptosis of BV173 cells and primary chronic myeloid leukemia cells, co-culture with mesenchymal stromal cells protected both types of chronic myeloid leukemia cells. Molecular analysis indicated that mesenchymal stromal cells reduced caspase-3 activation and modulated the expression of the anti-apoptotic protein Bcl-XL. Furthermore, chronic myeloid leukemia cells exposed to imatinib in the presence of mesenchymal stromal cells retained the ability to engraft into NOD/SCID mice. We observed that chronic myeloid leukemia cells and mesenchymal stromal cells express functional levels of CXCR4 and CXCL12, respectively. Finally, the CXCR4 antagonist, AMD3100 restored apoptosis by imatinib and the susceptibility of the SCID leukemia repopulating cells to the tyrosine kinase inhibitor.

Conclusions

Human mesenchymal stromal cells mediate protection of chronic myeloid leukemia cells from imatinib-induced apoptosis. Disruption of the CXCL12/CXCR4 axis restores, at least in part, the leukemic cells’ sensitivity to imatinib. The combination of anti-CXCR4 antagonists with tyrosine kinase inhibitors may represent a powerful approach to the treatment of chronic myeloid leukemia.     

Fanconi's anaemia presenting as acute myeloid leukaemia in adulthood

We describe a 28-year-old male patient who presented with apparently de novo acute myeloid leukaemia (AML) who was subsequently found to have Fanconi's anaemia (FA). The gene for complementation group A ( FAA ) has recently been localized to chromosome 16q24.3 and utilizing genetic markers closely linked to this locus we were able to conclude that this patient was likely to belong to complementation group A. FA presenting as AML is an exceptionally rare event and all previously described cases have occurred in patients less than 21 years of age. We conclude that the diagnosis of FA should always be considered in younger patients presenting with AML. It is important that the correct diagnosis is made in these individuals because the administration of conventional chemotherapy may well have devastating consequences for them. Correlations between the specific mutations causing FA and clinical phenotypes are likely to become apparent as more genetic analyses are performed in this group of patients.     

Prognostic significance of risk group stratification in elderly patients with acute myeloid leukaemia

Prognostic factors were studied in a series of 211 acute myeloid leukaemia (AML) patients over 60 years of age, treated at a single centre. The patients were allocated into three risk groups based on cytogenetics, occurrence of antecedent haematological disorder and leucocyte count. Only 3% had low-risk features, 39% had intermediate- and 58% had adverse-risk features. Complete remission (CR) was achieved in 43% of all patients. In multivariate analyses, the number of cycles needed to achieve CR and the risk group were significantly associated with the duration of CR. Median survival time for the entire cohort of patients was only 107 d. Advanced age, low induction treatment intensity, treatment during earlier years and adverse-risk group were associated with shorter overall survival times. Risk group classification may help selection of elderly patients with a good chance of benefiting from intensive treatment to actually receive such treatment, while sparing others with a low probability of survival benefit from toxic treatment. Low intensity induction treatment reduces the chance of obtaining complete remission, produces inferior survival times and should consequently be avoided when the aim is to obtain complete remission. In elderly AML patients, introducing age and re-evaluation of intermediate and good prognosis patients regarding response to induction treatment may improve the risk group classification.     

Epigenetics of paediatric acute myeloid leukaemia

Comprehensive cataloguing of the acute myeloid leukaemia (AML) genome has revealed a high frequency of mutations and deletions in epigenetic factors that are frequently linked to treatment resistance and poor patient outcome. In this review, we discuss how the epigenetic mechanisms that underpin normal haematopoiesis are subverted in AML, and in particular how these processes are altered in childhood and adolescent leukaemias. We also provide a brief summary of the burgeoning field of epigenetic-based therapies, and how AML treatment might be improved through provision of better conceptual frameworks for understanding the pleiotropic molecular effects of epigenetic disruption.     

Glutamate dehydrogenase 1: A novel metabolic target in inhibiting acute myeloid leukaemia progression

Glutamine metabolic reprogramming in acute myeloid leukaemia (AML) cells contributes to the decreased sensitivity to antileukemic drugs. Leukaemic cells, but not their myeloid counterparts, largely depend on glutamine. Glutamate dehydrogenase 1 (GDH1) is a regulation enzyme in glutaminolysis. However, its role in AML remains unknown. Here, we reported that GDH1 was highly expressed in AML: high GDH1 was one of the independent negative prognostic factors in AML cohort. The dependence of leukaemic cells on GDH1 was proved both in vitro and in vivo. High GDH1 promoted cell proliferation and reduced survival time of leukaemic mice. Targeting GDH1 eliminated the blast cells and delayed AML progression. Mechanistically, GDH1 knockdown inhibited glutamine uptake by downregulating SLC1A5. Moreover, GDH1 invalidation also inhibited SLC3A2 and abrogated the cystine-glutamate antiporter system Xc⁻. The reduced cystine and glutamine disrupted the synthesis of glutathione (GSH) and led to the dysfunction of glutathione peroxidase-4 (GPX4), which maintains the lipid peroxidation homeostasis by using GSH as a co-factor. Collectively, triggering ferroptosis in AML cells in a GSH depletion manner, GDH1 inhibition was synthetically lethal with the chemotherapy drug cytarabine. Ferroptosis induced by inhibiting GDH1 provides an actionable therapeutic opportunity and a unique target for synthetic lethality to facilitate the elimination of malignant AML cells.